1. Field of the Invention
The present invention is directed to the field of power plants. In particular, the present invention is directed to systems and methods for cooling a power plant using phase change materials.
The cooling towers for power plants generally consume a large amount of water. For example, in the year 2000, coal and gas power plants in the eight-state Interior West region of the United States withdrew over 650 million gallons of water per day, totaling over 728,000 acre-feet each year. That is enough water for the annual needs of at least 3.64 million people. Water in the West of the United States is becoming increasingly valuable especially in light of widespread drought conditions.
2. Description of Related Technology
Although agriculture is the largest water user in most of the United States, power production can have a large impact on the water supply and water quality in specific locations, especially in river basins that are already over-extended with other water uses. Large amounts of research have been devoted to design a cooling tower with a higher cooling efficiency and to reduce water consumption. For example, U.S. Patent Application Publication No. 2010/0018237 discloses a low water consumption cooling tower for gasification plants. The cooling tower comprises a wet section having a plurality of wet section fans and a dry section having a plurality of dry section fans. The wet section fans are adjustable to operate at different rates, depending upon ambient conditions surrounding the cooling tower. The wet section may comprise at least one shutter door. In operation, the wet section fans typically operate at an increased rate during a summer peak price period and at a reduced rate during a winter peak price period and an off-peak price period. The dry section fans operate at the increased rate all year. This method allows for less evaporative cooling and more latent cooling thereby reducing water consumption.
U.S. Patent Application Publication No. 2010/0154406 discloses a cooling tower system that exhibits increased energy efficiency. The cooling tower system includes a cooling tower unit, an expansion engine and a power operated component such as a fan or pump. The process fluid is first used to heat a working fluid for an expansion engine before being sent to the cooling tower for cooling. Power generated by the expansion engine is utilized to operate a component of the cooling tower such as a fan or a pump. The cooling tower is also utilized to provide cooling to condense the working fluid from vapor to liquid. The cooling tower removes waste heat from the process fluid.
U.S. Patent Application Publication No. 2013/0000867 discloses a hybrid cooling system for condensing an exhaust stream of a steam turbine. The cooling system comprises a dry cooling circuit, a dry air-cooled unit performing heat dissipation to cooling water flowing therein, and a wet cooling circuit and a wet cooled unit performing heat dissipation to the cooling water flowing therein. The cooling water flowing in the dry cooling circuit is separated from the cooling water flowing in the wet cooling circuit, and the dry and wet cooling circuits are connected to a common condenser. The hybrid cooling system reduces the evaporation and deposition losses of the wet cooling system, thereby reducing water consumption.
EP 2 498 037 A2 discloses a hybrid fan cooling tower apparatus that extends along a vertical axis. The cooling tower includes a first housing structure having an inlet and a first outlet located at a first position along the vertical axis, wherein the housing structure includes a base and opposing side walls that extend along the vertical axis away from the base. The tower also includes a heat exchanger disposed in the housing structure. The heat exchanger is positioned adjacent the first outlet and extends at least partially across the first outlet. The hybrid tower employs an air current generator positioned in a plane normal to the vertical axis and oriented to direct an air stream toward the base and through the heat exchanger and the first outlet.
Even with these improved cooling tower designs from the prior art, water consumption is still a major disadvantage for power plants throughout the world. The reliance on water places constraints on the location of power plants, which is currently limited to areas near a large body of water. Unfortunately, these areas are also densely populated, creating safety and pollution concerns. A cooling tower that reduces or eliminates water consumption will enable building of power plants in remote areas with little water available which are poorly suited for human living and agriculture.